In encoding an audio signal, quantization processing is performed for data compression. Encoding an audio signal is performed by utilizing, for example, a computer. In quantization processing, the quantization scale is corrected so that the spectral information of each channel has bits in the number of available bits or less determined by the bit rate and thus the quantization processing is completed. As a result, in the actual quantization processing, there is a case where the number of bits in quantization is smaller than the number of available bits and some bits are left unused.
On the other hand, as an audio signal, an audio signal capable of obtaining realism, such as stereo and 5.1 channel sound, is used widely, and therefore, each of a plurality of channels is encoded so that the total number of bits after the plurality of channels is encoded is smaller than the total number of available bits. In the encoding of the audio signal in the plurality of channels, effectively using of the bits left unused as described above has been sought. For example, improving the bit use rate in the total number of available bits by adding the bits left unused of the channel encoded previously to the number of available bits of a channel to be encoded later has been attempted.